1. Field of the Invention
The present invention relates to vessels for laying pipe and in particular to a stinger handling system for such a vessel. The invention also relates to the use of such a device in the deployment of a stinger.
2. Description of the Related Art
Pipelay vessels are generally known in various configurations. They may be broadly divided into three main principles of operation, namely J-lay vessels for deep water, near vertical pipe deployment, S-lay horizontal or low angle deployment and reel lay, where a continuous pipe is unwound from a reel. As the pipe is deployed from the vessel, it will tend to follow a catenary or similar curve towards the seabed, in order to provide the transition between this curve and the region onboard the vessel, a support structure is generally provided extending from the vessel and guiding the first portion of the pipe to its point of release. These support structures are known as stingers and for S-lay operation generally extend outwards from the stern of the vessel for considerable meters. Stingers may be constructed in sections and can be raised, lowered and extended as required. It is also generally necessary that the stinger can be completely removed e.g. after completion of the pipelay operation.
One device for stinger deployment is shown in US2012219362, which has a gantry construction over the stern of the vessel which supports the stinger by a cable. Use of a cable allows the gantry to support the weight of the stinger and the pipe but precludes however the absorption of compressive loads or uplift on the stinger or pipe. Increasingly, vessels are required to perform a multitude of functions including heavy lift operations. To this end, a heavy lifting crane at the stern of a vessel may sometimes be necessary. Clearly a heavy lifting crane cannot be located within the same space as a gantry for supporting the stinger. Another vessel is disclosed in WO05123566 having a heavy lift facility at the stern of the vessel. The crane includes a cable and winch arrangement at an elevated position on the crane body for supporting and lifting the stinger. A telescopic boom arrangement using hydraulic jacks is also contemplated.
While the existing devices and systems may be suitable for many circumstances, it would be desirable to provide a stinger handling system that is better integrated into the vessel structure and can be easily removed or stowed when not in use.